Pneumatic suspension systems of motor vehicles typically require air or gas to be supplied to inflatable or bellows-type springs at relatively high pressures, but at relatively low volume. A specialized pump or compressor is normally provided to produce an air flow with these characteristics, and the air suspension compressor is generally powered by means such as a direct current electrical motor dedicated to this purpose. For example, U.S. Pat. No. 4,738,454 to Watanabe, assigned to the assignee of the present invention and hereby incorporated by reference, discloses an air suspension system having an air compressor which may be mounted under the floor of the vehicle.
Conversely, the engine of the motor vehicle may require air at relatively low pressure and high volume for engine emission applications, particularly when excess air is needed during engine start-up conditions. Therefore, a compressor having operating characteristics different than those of the air suspension compressor, as well as its own power source, is conventionally required to supply engine air.